Power poles and telephone poles are conventionally formed from wood, steel or concrete and are pounded into the ground, or a hole is drilled into the ground and the pole is inserted into the hole.
Once the pole has been put into the ground, the upper part of the pole is arranged to receive power cables, data cables, telephone cables and the like. For some poles, the weight of these cables can be quite considerable and some poles contain additional devices such as power transformers which are quite heavy.
Wood rot, bores, termites and other factors operate to reduce the strength, and therefore, the service life of poles. For safety reasons, the strength of the poles must be periodically checked and the future life of the poles established. As wood rot generally occurs below the ground level, a simple visual inspection is not sufficient and mechanical strength tests must be carried out.
To date, no simple, efficient and reliable test method has been available so poles are often replaced well before the end of their effective life.
This naturally increases the operating expenses of the electricity authority.
A known method to test the strength of a pole is to apply a load to the pole. This is usually done using a hydraulic ram which pushes or pulls the pole. However, applying a pushing force or a pulling force directly to the pole using a ram or similar device has some disadvantages. Therefore, there would be an advantage if an improved method and apparatus could be provided to test a pole.
The inventor of the present invention has been particularly active in the past in devising methods and apparatus to test the strength of poles in order to determine fitness for the purpose to which they are put.
One of the methods for testing the pole strength uses a means to calculate the minimum required strength of the pole and load to be applied to the pole equivalent to the minimum strength, a means to apply a load to the pole, means to measure the load applied to the pole, and (a) means to calculate the residual strength of the pole from the applied load, or (b) means to measure the displacement of the pole under the applied load, means to calculate the residual strength of the pole from the applied load and the displacement, and means to detect the pole failure.
The prior art methods and apparatus test whether the pole possessed a predetermined minimum strength by simulating a maximum load for the predetermined strength. This generally produced a “yes/no” answer to the question whether the pole possessed the minimum strength or not. Generally, the prior art simulation applied a load that was equal to the maximum anticipated wind load on the pole multiplied by an appropriate safety factor.
During the course of developing and using the above method, the inventor discovered that the method and apparatus that was in use had drawbacks. The prior system required the establishment and use during the testing of a reference in order to measure the flexion or displacement of the pole. This reference became difficult to establish in difficult terrain, particularly when the ground is undulating or hilly.
Further, the method used was found to contain certain inaccuracies which could be improved upon. The inventor theorized that these inaccuracies may stem from the application of a load to the pole and the subsequent movement of the pole.
It will be clearly understood that, if a prior art publication is referred to herein, this reference does not constitute an admission that the publication forms part of the common general knowledge in the art in Australia or in any other country.